Surgical treatment of medically refractory epilepsy in childhood

Twenty-five percent of children with epilepsy continue to seize despite the best medical management and may be defined as medically refractory. Many children with medically refractory localization-related epilepsy, i.e. seizures which originate in a particular area of the brain and secondarily spread to involve other brain regions, may benefit from a variety of surgical treatments including hemispherectomy, corpus callosotomy, focal cortical resection of the temporal lobe, focal cortical resection of extratemporal regions of the brain, and multiple subpial resections. A successful outcome from epilepsy surgery is generally defined as a seizure-free state with no imposition of neurologic deficit. In order to achieve these twin goals two criteria must be fulfilled. First, precise localization of the epileptogenic zone in the brain is necessary. The epileptogenic zone may be defined as the region of epileptogenic cerebral cortex whose removal will result in a seizure-free state. Second, one must determine the anatomic localization of eloquent cortex in the brain in order to spare these areas during any planned cortical excision of epileptogenic cortex. Several diagnostic measures may be used to achieve a successful surgical outcome. A clinical history to ascertain the earliest symptom in the clinical progression of the seizure (semiology) is imperative as is ictal and interictal scalp EEG, neuropsychological testing, magnetic resonance imaging, positron emission tomography, single photon emission computerized tomography, and interictal magnetoencephalography. In the typical child undergoing evaluation for epilepsy surgery, if the clinical, neuropsychological, EEG, and radiological data are all concordant and point to the same area of epileptogenicity in the brain, cortical excision of the suspected epileptogenic zone is undertaken. However, if the data are discordant, and/or the epileptogenic zone resides wholly or in part within eloquent cortex, invasive intracranial monitoring from depth and/or subdural electrodes during a seizure is required to map out the areas of epileptogenicity in the brain. The assessment of potential risks and benefits for this type of epilepsy surgery in children involves complex age-related issues, including the possible impact of uncontrolled seizures, medication, or surgery on learning and development.